Composite telephonic and telegraphic circuit.



PATENTED FEB. 26, 1907.

Non 845,157.

G. M. YORK E. coMp sITE TELBPHONIG AND TELB'GRAPHIG CIRCUIT.

APPLICATION FILED JAN. '7, 1907.

@KMMN on) sraras arana crates} cnonce M. roam, or NEW YORK, 2;. Y., assroxon TO AMERICAN :TELE- PHOXEANDTELEGRAPH COMPANY, ACORPORATION oF-snW-Yo OOMPOSlTE TELEPHbNlC AND TELEGRflPHlC 'ClRCUlT.

To IL//- It'll/out 1 1 may concern:

Be it known that. l, (luconoi; M. Yonitn, residing at New York, in the county of New York and State 01 New York, have invented certain improvements in (oinpositc 'lelcphonic and 'lelegraphic (,ircuits, of which the following is a specification.

in composite systems of transmission cl that type in which two grounded lines, each having terminal telegra iii-stations, are bridged between said stations by conductors including telephone instruments to constitute a metallic telephone-oircuit it is customary to place in the bridges at opposite sides of the tele hone-stations condensers, which exclude irom the telephones the slowly-varying tfelegrapli-currents, while permitting practically the passage of the rapidlychanging voiee-tuirrents. 'lhis is shown in United States Patent No. 323,235), Van ltyssellwrghe, July 28 1885. in using this arrangenn-nt it was found that the operation of the two telegra ih-circuits caused such dill'crences of potential at the extremities ol the bridges that a How oi current occurred through the telephone instruments, which not only impaired their ellieiency, but also produced mutual interltwence between the telegraph-lines. 'lo obviate this dilliculty, the bridges have been connected to ground through a retardation-coil at each side ol the telcphone-station instruments and between them and the bridgo-condensers. While the impedance of the coilsprevented the passage of the telephone-ctirrents to ground, it gave for the disturbing currents points of approximately zero potential, so that interl'eronce with the telephones and telegraphic cross-interiercnce were both reduced. Now, though these earth branches excluded voice and magneto or like ringing currents when steady signaling-ourrents, such those of central-energy systems, were applied to the telephone branc ies they found free paths to ground. i To overcome this, condensers were inserted in the bridges between the instruments and the points of connection of the earth branches, thus confining the steady signallug-currents to the portions ol the branches contain'ng the telephone :instruments, .but'still a lowing the voice-currents and pulsatory signalingcurrents to pass out over the line.

. 'l he amount of condenser capacity which Specification of Letters Patent.

Application filed January 7. 1907. Serial No. 351.231.

Patented. Feb. 26, 1907.

should be placed in series between the telegraph-lines and the telephone instruments to,

give good telephonic transmission is controlled by two considerations-At must, be sulliciontly great to enable voice-currents to pass without material impairment and yet be so small that tclegrapl'ncurrents are substantially excluded. it has been foundin' practice that a capacity of about two microl'arads is most etl'ectivc. in the first arrat'igcn'ient oi the composite system men tioned a single two-microi'arad condenser was placed in the bridge at each sideof the telephone instruments. 1 herefore when the ground branches were added and the condensers to keep from them the steady signaling-currents it was found necessary to give each condenser a capacity of four micr0 t'arads, so that the total value in series .be-' tween the telephone instruments and the telegraph-line might remain at two microl'arads. mission was attained, but at the expense of telegraphic transn'iission, since there was in the condensers between the lines and the ground branches a grounded capacity of our microfarads for each line and at each bridge where beiore there was only two micro in this way good telephonic transgrammatically an application of my inventron, there being a single figure shown in separated sections for convenience in illustrat'ton.

lane condmwtors L L extend between pairs of terminal telegraph-stations A B and A} W, at which they are grounded, said stations being equipped with the apparatus usua lin composite systems. Bet-ween the telegraph-stations conductors 10 and '11 bridge the lines and'load into telephone-stai tions C C fi'respectively, which are thus connected by a metallic circuit furnlshed by the bridges and intermediate portions of the two telegraplrlines. 'lhe telegraph currents must be barred from .the telephone instruments, and to direct this and at the same time allow the passage of telephone-currents condensers c are included in each bridge I conductor between its junctures'with the dine conductors at a b and a b and the telephone instruments. while being freely permissive to telephonetively, that would tend to cause pulses of inductive resistancei is placed in each earth companion. telegraph-line.

- standard telephone-circuits comprising toll show the apphcationof this invention.

' contacts of a jack j, 'with which cooperates :1.

' plugY-p for cooperation with a jack 7', to

' controlling upon its front contact the local 14 at the toll-operators position E.

These condensers,

currents, should practically exclude the slowly-varying telegraphic impulses, and,

the Capacity which has been found to best perform this double function is about twol microfarads for each condenser. I There will, 1 however, in the operation of the telegraphlines be fluctuating differences of potential between the points a b anda 6*, respeccurrent to traverse the bridges, disturbing the telephone instruments and giving crossinterferenee between the telegraph lines. To avoid this, earth branches 1,2.are joined to the bridgeronductors at points d between the condensers c and the telephone instruments, they being grounded in pairs at g through'common conductors 13. A suitable The telephone-station associated with the bridge-conductors may and under the present practice usually would be of a type in which a common battery is employed, the steady current from which in operating lamp-signals and the like would have access to the"bridge-conductors. In the present instance there are illustrated portions of and switching". cord-circuits, intcrollice trunks, and subscribers hnes, only such elements being retalned as are'necessary to .The bridges 10 and 11 each include the plug p, terminating one end of a cord-circuit At the opposite end of the toll-cord a plug p adapted to engage a jack 7', connected by'a trunk-circuit 15 through a repeating-coil c to the cord-circuit 16' of a switching-operators position at F. The switching-cord has a which is connected a subscribers line 17, having the usual substation set s. The tollcord circuit has bridged across it a relay r,

circuit 18 of a lamp Z, said circuit including a normally closed contact in the toll-operators listenin -key k. Associated with the switching-corril 1 6 is a double-wound relay r", having' a winding included in a conductor 19, leading from the free pole of a grounded battery f throu h one armature and back contact of a re ay 1" to the-trunk 15, thence through the jack 7' and plug 1), the toll-cord .14, re plug, trunk, conductor 20, and another armat me and back contact of relay r to ground through theesepond winding. of the relay T3. The winding of therelayflisgonnectgl from ground through the normally opFffroniRion-j' tact of a relay 1", having its Winding in one side of the switching-operators cord and through the front contactand armature of relay r to the free pole of battery Considering for the purposes of thisdescription that the call to be handled is incoiu ing to the telephone-ollice C, the plug 0 would first 'be placed in the jack by the toil operator, who after communicating with the switching operator over an order-wire (not ay 1', and back through the cord, jack,

shown) would insert the plug 11 in the desighated jack j ceded by the placing by the switching operator of LllC plug in the jack j; -The called subscriber should now be rung by the toll operator, and she is apprisedot the-fact and governed 1n discontinuing the ringing by the lhis.would have been pre' lamp Z, which receives current from its local hat Lory afterthc relay 1" has drawn up its armature, The actuation oi this relayr occurs after 1i ass-:ociation of the plu 1) and jack j by currentl'rom the battery over the circuit previously indicated and including the tollcord, trunks, and conductors l9 and 20.

'lherclays 1' and 1- which act'to extinguish the lamp Z n )011 the removal of the receiver from the hoo at the called substation, do not (roncern the present inventlon and need not he lurther considered.

it will be seen that if the brid e 10 and its earth branches 12 were arrange has been fl described a shunt would be placed upon the relay 1', and the relative resistance would be such that the lamp 1 would not light. To

prevent this, condensers c are placed in the earth branches, preferably each having a capacity of about two Imcrofarads. These 1mpassably bar the steadylcurrent flowing from the battery f, and'the rela r o crates Without interference. On the ot er and, v the tres-f, passing telegraph-currents, whlch have.

already passed the condensers'c, readily pass throu the condensers c to ground As has been previously indicated, the condensers c might be placed in the brid e-con-w ductors 10 andll', as shown in dotted ines at 1;, between the points 1 and the telephone instruments and the desired result in-aimeasure secured; but by the arrangement here described important advantages are gained. If

the condensers were'inserted in the bridge at f c, to get that capacity oftwo microfarads,

which gives ihost eflicient telephonic transmission, one must make 0 and c of four 1111 crofarads each, thus giving in series ones'half this amount, and then We should have con nected. with each line at each bridge a grounded capacity of four microfarads furnished by the condensers c, and this total of sixteen mierotarads added to the capacity of the lines themselves would materially impair telegraphic transmission. The present invention places between the lines L and L at a, a 7), and b and the earth at 9 two capacities c and c of two inicrofarads each in series, or one microfarad, increasing the total capacity of both lines but four inicrofarads. At the same time it should be remembered that we have the standard capac ity of two microfarads in the bridges at each side of the telephone-offices.

Furthermore, my improved system re duces both the disturbance in the telephone instruments and the mutual interference between the telegraph-lines, for though the impedance of the earth branches has been increased by the placing of the condensers c therein rather than in the bridges, which in itself would tend to augment these dillieulties by shunting more current through the tele phone apparatus, the total impedance of the paths from a to b and from a to b and from each of the points a, 1), a and b to earth is increased. This follows because although the total capacity of the bridge-conductors passing through the telephone-o'llices remains the same (approximately one microtarad) that of the paths from a, 1), a and Z1 to ground is one mierot'arad instead of tour niicroiarads, so that the impedance as a whole to the slowly-varying currents entering the bridge is increased to a much greater extent than the increase in the relative impedance oi the earth branches to that portion of the bridgeconductors within the points (15. 'llierelore a considerably-reduced telegraph current passes the condensers c, and the disturbing portion, or that traversing the bridge-com ductors from d to a, is less. than it the con densers 0 were between these points and the telephone-ell'iccs Having thus described my invention, I claim 1. A composite telegraph and telephone system comprising line conductors provided with telegraph-stations, intermediate bridgeconductors connecting the lines and containing telephone instruments, said instruments having associated with them sources of steady current having access to the bridge-conductors, earth branches joined to the bridges at each side of the telephone instrumci'its, and means situated iii' the earth iHtlIlCliOSlOl' preventing the passage ot'st ady currents.

2. The combination with line conductors having tcrn'iiiial telegraph-s1ations, ol bridgeconductors connecting the lines and leading totelephoneinstruments,condensersincluded in a bridge at each side oi the telephone instruments, earth branches joined to said bridge between said condensers and the telephone iiistrnmei'its, and a condenser in each earth branch. p

3. In a composite telegraph and telephone system, the combination with line (OlltltHr tors provided with terminal telegraph-stations, of bridge-conductors connecting the lines and lcadii'ig to telephone-sinlions, said telephone-stations having sourccs oi steady signaling-currci'it which may be connected with the bridges, condensers included in the bridges at each side of the telcphonc-stations and being of such capacity as to most efl'cct- 'ivclv exclude tclcgraph-currcnts while permitting the tree passage of telephone-cur rents, earth branches ]()lii(tl to the bridges between said condensers and the telephonestations, and a condenser in each tarth branch, substantially as described.

in testimony whereof I have signed my name to this sywcnicrttion, in the presence oi two subscribing witnesses, this 4th day or January, 1907. (llGOltG-ll M. itiltlil l.

Wit ncsscs:

lCnwAnn Bin-runner,

W. E. ATUEARN. 

